So, I have Canon XSi and the only real complaint I have is that the camera is kinda small and I prefer the ergos of 40D much better. Other than that, I am perfectly happy with the camera, well may be I wouldn't mind to have 3200 ISO setting

I looked at reviews and saw that it's faster fps, weather proofed somewhat, more solid camera, better AF points. What I will miss is the 2 MP - going down from 12 to 10.

I was wondering what are other comparisons - like do I get better High ISO performance in comparison to XSi.

i am being offered a good deal on almost new 40D, so I will not spend more than $100 after I sell my xSi.

Why will you miss those 2 MP? How big are you enlarging your pictures?

The lowering of the MPs means that each pixel on the sensor is bigger, as there are less to put on the sensor. So a bigger pixel on the sensor would mean that they can be more sensitive to light, hence the higher ISO and better quality at high ISO.

Same argument comes up when people look at the 40D and an upgrade to the 50D. The 50D has more MP, but is not as good in low light (or so I have been told) due to the more pixels on the same sensor thing.

Being the current owner of an XSI, one who debating between the 40D and the XSI 7 months ago when he purchased, not knowing much about cameras, I regret not going with the 40D and would consider the 40D as a nice upgrade to my XSI.

Also, going from XSI to a full frame camera may mean that you have to buy new lenses &#8211; depending on what you have already with your XSI. If you have EF-S lenses with your XSI, those won&#8217;t work on the full frame cameras, but will work on the 40D / 50D.

If you are liking the bigger feel of the 40D, then you can always look into getting a battery grip for your XSI&#8230;the BG-05. About $200 CAD.

agree the 50D has not got increased ISO capabilities over the 40D, but it is offering a massive increase in MP at the same ISO levels - which is an achivement in itself.
I have read, however, that with the resolving power of the 50D it generally only performs best when used with pro end glass.

As for the OP firstly I would encourage you to check 2 things first

1) if size is important try getting a battery grip for the XSi - that might make it easier to hold for you. The added battery slot and controls also make it a good adition to a setup.

2) I (nearly always) recomend a user upgrade their glass (lenses) to the best they can before upgrading a camera body. If you are going to upgrade the body make sure your upgrading for key aspects which will expand your photography and quality of images

As for the 40D as an upgrade I have spoken to many photographers that have upgraded from the rebel series cameras to a 40D and found it to be a worthy camera to upgrade to

Thanks for your opinions, I already upgraded my glass to what I feel will work for my use of the camera - see my signature.

well, the camera I was looking at didn't work out - there was some dirt on the mirror, the owner was not a pleasant personality and I had my doubts about how upkept the camera was. I will be looking for more, for now, my Xsi will serve me well

i cant say anything for the xsi, but ive got a 40D i can say its definitely and excellent camera, i probably wouldnt go for the 50D, its only got minor upgrades and isnt really worht the extra money if you can get a good deal on a 40D

Also, going from XSI to a full frame camera may mean that you have to buy new lenses  depending on what you have already with your XSI. If you have EF-S lenses with your XSI, those wont work on the full frame cameras, but will work on the 40D / 50D.

Also, going from XSI to a full frame camera may mean that you have to buy new lenses  depending on what you have already with your XSI. If you have EF-S lenses with your XSI, those wont work on the full frame cameras, but will work on the 40D / 50D.

I didn't say the 40d/50d are full frame, I said going from XSI to full frame will make EF-S lenses non compatible, but the same EF-S lenses will work on the 40d/50d.

Poorly worded on my part, and very misleading when I read it over.
XSI, 40D, 50D = crop sensors that work with EF-S and EF lenses
5d, 1d = full frames that will NOT work with EF-S lenses but work with EF lenses